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| 2. |
- Lousen, B., et al.
(författare)
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Compressing a Non-Planar Aromatic Heterocyclic [7]Helicene to a Planar Hetero[8]Circulene
- 2020
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 26:22, s. 4935-4940
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Tidskriftsartikel (refereegranskat)abstract
- This work describes a synthetic approach where a non-planar aromatic heterocyclic [7]helicene is compressed to yield a hetero[8]circulene containing an inner antiaromatic cyclooctatetraene (COT) core. This [8]circulene consists of four benzene rings and four heterocyclic rings, and it is the first heterocyclic [8]circulene containing three different heteroatoms. The synthetic pathway proceeds via a the flattened dehydro-hetero[7]helicene, which is partially a helicene and partially a circulene: it is non-planar and helically chiral as helicenes, and contains a COT motif like [8]circulenes. The antiaromaticity of the COT core is confirmed by nucleus independent chemical shift (NICS) calculations. The planarization from a helically π-conjugated [7]helicene to a fully planar heterocyclic [8]circulene significantly alters the spectroscopic properties of the molecules. Post-functionalization of the [7]helicenes and the [8]circulenes by oxygenation of the thiophene rings to the corresponding thiophene-sulfones allows an almost complete fluorescence emission coverage of the visible region of the optical spectrum (400–700 nm).
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| 3. |
- Pedersen, S. K., et al.
(författare)
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Dianthracenylazatrioxa[8]circulene : Synthesis, Characterization and Application in OLEDs
- 2021
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 27:45, s. 11609-11617
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Tidskriftsartikel (refereegranskat)abstract
- A soluble, green-blue fluorescent, π-extended azatrioxa[8]circulene was synthesized by oxidative condensation of a 3,6-dihydroxycarbazole and 1,4-anthraquinone by using benzofuran scaffolding. This is the first circulene to incorporate anthracene within its carbon framework. Solvent-dependent fluorescence and bright green electroluminescence accompanied by excimer emission are the key optical properties of this material. The presence of sliding π-stacked columns in the single crystal of dianthracenylazatrioxa[8]circulene is found to cause a very high electron-hopping rate, thus making this material a promising n-type organic semiconductor with an electron mobility predicted to be around 2.26 cm2 V−1 s−1. The best organic light-emitting diode (OLED) device based on the dianthracenylazatrioxa[8]circulene fluorescent emitter has a brightness of around 16 000 Cd m−2 and an external quantum efficiency of 3.3 %. Quantum dot-based OLEDs were fabricated by using dianthracenylazatrioxa[8]circulene as a host matrix material.
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| 4. |
- Preus, S., et al.
(författare)
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The photoinduced transformation of fluorescent DNA base analogue tC triggers DNA melting
- 2013
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 12:8, s. 1416-1422
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Tidskriftsartikel (refereegranskat)abstract
- While fluorescent analogues of the canonical nucleobases have proven to be highly valuable in a large number of applications, up until today, fluorescent DNA base analogues remain virtually inapplicable for single-molecule fluorescence experiments which require extremely bright and photostable dyes. Insight into the photodegradation processes of these fluorophores is thus a key step in the continuous development towards dyes with improved performances. Here, we show that the commercially available fluorescent nucleobase analogue tC under intense long-term illumination and in the presence of O-2 is degraded to form a single photoreaction product which we suggest to be the sulfoxide form of tC. The photoproduct is characterized by a blue-shifted absorption and a less intense fluorescence compared to that of tC. Interestingly, when tC is positioned inside double-stranded DNA this photodriven conversion of tC to its photoproduct greatly reduces the duplex stability of the overall double helix in which the probe is positioned. Since tC can be excited selectively at 400 nm, well outside the absorption band of the natural DNA bases, this observation points towards the application of tC as a general light-triggered switch of DNA duplex stability.
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| 5. |
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| 6. |
- Hillers-Bendtsen, A. E., et al.
(författare)
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Modeling Absorption and Emission Spectroscopies of Symmetric and Asymmetric Azaoxahelicenes in Vacuum and Solution
- 2022
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 126:37, s. 6467-6472
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Tidskriftsartikel (refereegranskat)abstract
- Helicenes are of general interest due to the significant chiral signals in both absorption- and emission-based spectroscopy. Herein, the spectroscopic properties of four recently synthesized azaoxahelicenes are studied using density functional theory methods. The azaoxahelicenes have 7, 9, 10, and 13 units and one to two complete turns of the structure. UV-vis absorption and electronic circular dichroism spectra are determined both in vacuum and in solution using explicit solvation through a combined molecular dynamics/polarizable embedding framework. Additionally, emission and circularly polarized luminescence spectra are determined based on vibronic calculations. The resulting spectra are in good agreement with the experimentally available data, highlighting that both absorption- and emission-based spectra of the systems can be modeled computationally such that reliable predictions can be made for systems that are yet to be synthesized.
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| 7. |
- Ivaniuk, K. B., et al.
(författare)
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New WOLEDs based on pi-extended azatrioxa[8]circulenes
- 2017
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 5:17, s. 4123-4128
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Tidskriftsartikel (refereegranskat)abstract
- New stable WOLEDs based on pi-extended azatrioxa[8]circulenes have been fabricated. Combining the own blue emission of the azatrioxa[8] circulenes with the yellow-green emission of the "m-MTDATA:azatrioxa[8]circulene'' exciplex a broad visible region, from 400 to 700 nm, is covered. The so constructed WOLEDs exhibit a luminance exceeding 23 700 cd m(-2) and an external quantum efficiency reaching 3%.
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| 8. |
- Minaeva, V. A., et al.
(författare)
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Experimental and theoretical study of IR and Raman spectra of tetraoxa[8]circulenes
- 2012
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Ingår i: Vibrational Spectroscopy. - : Elsevier BV. - 0924-2031 .- 1873-3697. ; 61, s. 156-166
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Tidskriftsartikel (refereegranskat)abstract
- The FTIR and Raman spectra of symmetrical derivatives of the tetraoxa[8]circulenes (D 4h symmetry) series have been detected and the experimental data have been interpreted by density functional theory (DFT). The equilibrium molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities of the studied tetraoxa[8]circulenes have been calculated by the DFT/B3LYP method with the 6-31G(d) basis set using the symmetry constrains. Comparison of the calculated vibrational spectra with the experimental data provides reliable assignments of all observed bands in FTIR and Raman spectra, including the low frequency region. Correlation diagrams with symmetry account of vibrational modes in the studied molecules and their constituents (benzene, naphthalene and furan) have been used and proven very useful in the force field and frequency analysis. The results of quantum-chemical calculations are in excellent agreement with all details of the experimental spectra.
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| 9. |
- Minaeva, Valentina A., et al.
(författare)
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The FTIR spectra of substituted tetraoxa[8]circulenes and their assignments based on DFT calculations
- 2013
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Ingår i: Vibrational Spectroscopy. - : Elsevier BV. - 0924-2031 .- 1873-3697. ; 65, s. 147-158
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Tidskriftsartikel (refereegranskat)abstract
- The FTIR spectrum of symmetrical derivative of the tetraoxa[8]circulene, named para-dinaphthyleno-2,3,10,11-tetraundecyldiphenylenotetrafuran (p-2B2N4R, R = n-C11H23) has been recorded and interpreted using density functional theory (DFT) calculations for the model compounds p-2B2N4R (R = H, C2H5). The unsubstituted tetraoxa[8]circulene, namely para-dinaphthylenodiphenylenotetrafuran (p2B2N) and para-dinaphthyleno-2,3,10,11-tetraethyldiphenylenotetrafuran (p-2B2N4R, R = C2H5) belong to the D-2h and D-2 symmetry point groups, respectively. The equilibrium molecular geometry, harmonic vibrational frequencies and infrared intensities have been calculated utilizing the DFT/B3LYP method with the 6-31G(d) basis set using the symmetry constraints. Comparison of the calculated vibrational spectra with the experimental data provides a reliable assignment of the observed bands in the FTIR spectra. The results of quantum-chemical calculations provide a complete interpretation of vibrational modes based on a good agreement with all details of the experimental spectra.
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| 10. |
- Pedersen, S. K., et al.
(författare)
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Anti-Aromatic versus Induced Paratropicity : Synthesis and Interrogation of a Dihydro-diazatrioxa[9]circulene with a Proton Placed Directly above the Central Ring
- 2020
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:13, s. 5144-5150
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Tidskriftsartikel (refereegranskat)abstract
- We present a high-yielding intramolecular oxidative coupling within a diazadioxa[10]helicene to give a dihydro-diazatrioxa[9]circulene. This is the first [n]circulene containing more than eight ortho-annulated rings (n>8). The single-crystal X-ray structure reveals a tight columnar packing, with a proton from a pendant naphthalene moiety centred directly above the central nine-membered ring. This distinct environment induces a significant magnetic deshielding effect on that particular proton as determined by 1H NMR spectroscopy. The origin of the deshielding effect was investigated computationally in terms of the NICS values. It is established that the deshielding effect originates from an induced paratropic ring current from the seven aromatic rings of the [9]circulene structure, and is not due to the nine-membered ring being antiaromatic. UV/Vis spectroscopy reveals more efficient conjugation in the prepared diazatrioxa[9]circulene compared to the parent helical azaoxa[10]helicenes, and DFT calculations, including energy levels, confirm the experimental observations.
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